Apparatus for drying pulp-insulated wire

ABSTRACT

A plurality of pulp-insulated wires are continuously dried in a heated chamber of a drying oven having a system for continuously changing the drying atmosphere. Preheated air is continuously introduced to an input end of the chamber and moisture-laden gases are continuously exhausted from the chamber at positions spaced along its length. The input air is blown over ducts which carry the hot gases away from the chamber. Input air is thus preheated prior to entering the drying chamber. Use of a preheated air drying system permits an overall reduction in operating temperature of the drying chamber with a result that the pulp-insulation on the wire is provided with improved breaking strength and elongation properties.

United States Patent 1 91 1111 3,829,985

Dunn et al. Aug. 20, 1974 [5 APPARATUS FOR DRYING 3,403,454 /1968 Smith34/155 PULPJNSULATED WIRE 3,491,457 1/1970 Schreiber et a1... 34/13,604,824 9/197] Hardison 34/155 entors: Helmut E. Durr, Chatham; Albert3,616.459 10/1971 Patton et al. 34/1 H. Haller, Clark, both of NJ.Primar ExaminerCarroll B. Dorit Jr. [73] Ass1gnee: Western ElectricCompany, y

Incorporated New York, gttfiaerlrlziery, Agent, or F1rm-P. J. Tr1bulsk1,Jr.; W. O.

c [22] Filed: June 23, 1972 21 Appl. No.: 265,920 [57] ABSTRACT Aplurality of pulp-insulated wires are continuously dried in a heatedchamber of a drying oven having a [22] }J.S.(gl. 34/115246, 3121(5)?)System for continuously Changing the drying atmo b Sphe p e e air is Cosly introduced to an [58] Bed of Search 34/23 3 input end of the chamberand moisture-laden gases .19/1 are continuously exhausted from thechamber at positions spaced along its length. The input air is blown[56] References Cited over ducts which carry the hot gases away from theUNITED STATES PATENTS chamber. Input air is thus preheated prior toentering 1,418,386 6/1922 Maus 34/27 the drying chamber. Use of apreheated air drying sys- 1,432,270 10/1922 Walsh 34/82 tem permits anoverall reduction in operating temper- 1945,35l 2/1934 Freeland 34/155ature of the drying chamber with a result that the gr pulp-insulation onthe wire is provided with improved pern e a 2,804,694 9 1957 Clipsham34/155 breakmg strength and elongano" propemes' 3,041,736 7/1962Peterson et al. 34/23 1 Claim, 4 Drawing Figures F/G. (PRIOR ART)mEmEm-mn 3.829.985

a or z 26 AWG 22AWG A (AVERAGE (AVERAGE) VALUES VALUES PRIOR BREAKINGSTRENGTH 3.85 LBS. 7.72 LBS.

ART ELONGATION |.5| v.45

IMPROVED BREAKING STRENGTH 4.53135 QJOLBS DRYER ELONGATION [.86 1.73

APPARATUS FOR DRYING PULP-INSULATED WIRE BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to improvements in themanufacturing of pulp-insulated wire. More particularly, the inventionrelates to an improved system for drying pulp-insulated wire on acontinuous basis.

2. Description of the Prior Art Pulp-insulated wire is typicallyproduced by a continuous process in which many wires are insulatedsimultaneously. A plurality of wires, often as many as 60,'aresimultaneously coated with a wet pulp layer and are then drawn through adrying oven in order to produce a final dried pulp insulating coating oneach of the wires. A thorough description of a pulp-insulating processcan be had by referring to Manufacturing Pulp Cable," The WesternElectric Engineer, (June-October temperature is usually maintained atapproximately 900F. A natural draft vent system is provided at theoutput end to permit water vapor to escape from the system.

Successful and efficient operation of drying ovens of this sort dependson a delicate balance between the operating temperature and the amountof air flow through the heating chamber. If air flow is decreased tooseverely by closing the vent, there will develop an excessive build-upof water vapor within the chamber and a consequent loss of efficiency.If the vent is opened too far, an excessively high rate of air flow willcause a reduction in operating temperature which will also result in aloss of efficiency of the oven. These problems become particularly acuteon hot and humid days.

In order to strike a balance between these conflicting considerations,the initial heating zones of the chamber are usually operated at atemperature which is undesirably high. When wet pulp-insulation isexposed to a particularly high temperature, the water in the pulpexpands very rapidly and as a result, the-elongation properties andbreaking strength of the final pulp-insulation are diminished.

In general, a reduction in temperature require either a slower speed oftraverse for the wire or a longer oven consuming more valuablemanufacturing floor space. Each of these alternatives are economicallyundesirable. Further, it is desirable that the pulp insulation haveimproved breaking strength and elongation properties.

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto provide an improved drying oven for pulp-insulated wire which willpermit efficient and economical operation at lower temperature thanthose used on prior-art ovens.

It is also an object of the invention to provide an oven wherein thehumidity within a heating chamber can be carefully controlled to permitefficient operation.

These and other objects are achieved by providing a drying oven whereinthe atmosphere within a heating chamber is positively and continuouslyreplaced with preheated air. This results in an overall reduction in theoperating temperature of the chamber and improved tensile and elongationproperties in the final pulp insulation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 3 is a sectional view taken alongthe lines 3-3 of the drying oven of FIG. 2; and

FIG. 4 is a chart showing numerical values of improved propertiesassociated with use of the inventive drying-oven, atmosphere-controlsystem of FIG. 2.

DETAILED DESCRIPTION A drying oven, designated generally by the numeral20 and shown in FIG. 2, is basically a modification of a prior artdrying oven, designated generally by the numeral 22 and shown in FIG. 1.Comparing FIGS. 1 and 2, it can be seen that a natural draft ventarrangement 24 has been removed from the oven 22 and has been replacedwith a forced draft venting system.

The venting system of oven 20 includes a plurality of vent stacks 26which form a connection from a heating chamber 28 to an exhaust manifold30. A fan 32 draws air .from the exhaust manifold 30 and drives it to anexhaust vent 34. Wires 36, having wet pulp applied on their surfacesenter the oven 20 at an input side 38 which is on the right side of theoven. The wires 36 pass through the heating chamber 28 which issurrounded by electric heating coils 40. The heating coils 40 arecontrolled thermostatically to provide three separate zones of heat,designated in FIGS. 1 and 2 as zones A, B and C.

It has been found that zones A and B can be operated at a temperature ofapproximately ll5014 l200F. Zone C can be operated at a temperature ofapproximately 900F.

Gases from the heating chamber 28 are drawn upwardly through the ventstacks 26 and are discharged through the exhaust vent 34. Make-up air isprovided from the ambient atmosphere through a fan 42 and an input airduct 44. The duct 44 surrounds the vent stacks 26. This arrangementpermits the relatively cool input air to be preliminarily heated bypassing over the relatively hot vent stacks 26. The input air duct 44 isalso provided with an auxiliary electric heater 46 which is used toassure that the input air entering the heating chamber 28 is raised to atemperature of at least 900F.

The fans 32 and 42 are controlled to provide a flow speed of air ofapproximately 6-7 feet per second through the heating chamber 28.Additional control of air flow is achieved by varying the opening of adraftcontrol port 48. Typically, the chamber 28 has a length of about 27feet. This means that the atmosphere within the chamber is completelyexchanged at a frequency of at least 12 times per minute.

The exchange of atmosphere within the chamber 28 can take place withgreat rapidity, because the makeup air being introduced with the inputside 38 of the chamber is preheated. Thus, the drying oven can beoperated efficiently with relatively low temperatures in zones A and Band with the consequent result that the breaking strength and elongationproperties of the final insulated wire 36 are improved. By referring toFIG. 4 one can see the tabulated results of the improved properties. Thevalues shown in association with the term Prior Art are obtained throughuse of an oven of the type which is shown in FIG. 1. The valuesassociated with the term, Improved Drying are obtained through use ofthe oven 20, shown in FIG. 2.

Although certain embodiments of the invention have been shown in thedrawings and described in the specification, it is to be understood thatthe invention is not limited thereto, is capable of modification and canbe arranged without departing from the spirit and scope of theinvention.

What is claimed is:

1. In a drying oven for continuously drying pulpinsulated wire, the ovenhaving an open-ended heating chamber divided into at least two zones,heating elements located in each of the zones, means for moving wireinto an input side of the chamber and in sequence through each of thezones and past the heating elements, and means for separatelycontrolling the heat output of the heating element in each of the zonesto establish a separate, predetermined temperature in each of the Zones,the improvement which comprises:

L566-PT UNITED STATES :PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3.829.985 I Dated Aflgnqi' 9n; 107A lnventbr(s) n mug mrgvagd Albgg;H,- Ha11er 7 It is certifiedfghat error appears inrhe above-identifiedpatent and that said Letters Patent are herebyfcbrrected as shown below:

Column 2; line 47, "115o14 12o0F" should be --1-15"0-120 0F--.

Signed arid sealed this 19th day pf November 1974.

(SEAL) Attest:

c. MARSHAILLJDANN Commissioner of Patents MCCOY M. GI SON JR. AttestingOfficer

1. In a drying oven for continuously drying pulp-insulated wire, theoven having an open-ended heating chamber divided into at least twozones, heating elements located in each of the zones, means for movingwire into an input side of the chamber and in sequence through each ofthe zones and past the heating elements, and means for separatelycontrolling the heat output of the heating element in each of the zonesto establish a separate, predetermined temperature in each of the zones,the improvement which comprises: means for replacing water vapor withinthe chamber with air, including a duct for supplying air to the inputside of the heating chamber, a series of vent stacks distributed alongthe length of the chamber, and means for drawing gases through the ventstacks from the heating chamber; and means for preheating the air,including portions of the vent stacks, located within the duct totransfer heat from the gases drawn from the chamber to the air in theduct, and including an auxiliary heater to further heat the air prior toits introduction into the chamber.